Process of making aliphatic polyureas



Patented Jan. 31, 1939 2,145,242

UNITED STATES PATENT OFFICE Harold Wilfred Arnold, Wilmington, Del.,assignor to E. L du Pont de Ncmours & Company, Wilmington, M, acorporation of Delaware No Drawing. Application July 2, 1937, Serial No.151,768

11 Claims. ((1280-5550 .his invention relates to amides and moreparradical. the products are quite diiferent from .cularly to ureas.those obtained with the types of amines just dis- This invention has asits chief object the procussed. Instead of being resinous polymers, theyvision of a novel, convenient and economical are definite crystallinemonomeric compounds of process for the preparation of ureas. More spetheformula NHz-CO-NHlft-NHCONH2 cifically it relates to and has as anobject the in which R is the divalent aliphatic radical-origipreparationof aliphatic polyureas, in particular nally in the amine between the twoamino groups. aliphatic diureas of the comprehensive formula That thistype of compound, instead of a resinous H2NCO-NHRNHCONH:, wherein Rpolymer or 1 a symmetrical bis-monoalkylurea,

is a divalent aliphatic hydrocarbon radical conshould be formed is verysurprising in view of the 10 taining a. chain of at least two carbonatoms bemanner in which urea is known to combine with tween the nitrogenatoms. I aliphatic monoamines. As already pointed out,

The above and other objects appearing hereinthe latter amines yields-dialkyl ureas only, that after are accomplished by the followinginvention is each molecule of urea reacts with two amine wherein urea isreacted, by heating, with an aligroups, whereas in that part of thepresent 15 phatic polyamine having at least. one hydrogen processinvolving primary diamines of the stated atom attached to each of twoamino-nitrogen type each molecule of urea reacts with only one atoms,more particularly with a primary diamine amine group. Expresseddifferently, it is surin which the amino groups are separated by anprising that definite crystalline-monomeric com- I aliphatic hydrocarbonradical having a chain of pounds instead of resinous polymers are formed20 at least two carbons between the nitrogen, and in this reactionbetweentwo bifunctional comstill more particularly with apolymethylenedipounds, yet this phenomenon is true even when amine.proportions are varied over wide ranges (com- It is known from U. 8.Patent 1,785,730 that pare Examples I and II below). urea combines withprimary aliphatic mono- In carrying out the preferred embodiment of 25amines to form s-dialkylurea without detectable this invention,discussed above, the urea is heated amounts of monoalkylureas. However,insofar as ith the aliphatic primary diamine to reaction is known, ithas not been proposed to react urea temperature, the heating continueduntil no more with aliphatic polyamines of the above type. It ammonia isevolved, and the polyurea isolated by has now been discovered that thesecompounds crystallization from a solvent wherein the poly- 30 willcombine readily, a variety of useful aliphatic urea is soluble atelevated temperature but relapolyureas being obtained. tively insolubleor only slightly soluble at ordi- The character of the aliphaticpolyurea pronary temperatures. The net reaction may be repduced in theprocess of this invention depends on resented by the following equation,wherein .r

the type of amine employed. When amines havis a positive integer of atleast 2:

35 ing hydrogen attached to each of three or more amino nitrogens,especially those of the formula I! NH2[(CH2)eNH]y(CI-I2)NH2 wherein a:and y are 5- positive integers, are reacted with urea, for ex- Ii 7 ll Y40 ample at temperatures in the range of 120 C. to 40 160 C., there areobtained thermoplastic resinous The more detailed Practice of theinvention is polymers soluble in alcohols, ketones, and esters,ulusl'llated by the following examples, w e ein insoluble inhydrocarbons, and limitedly soluble D s given are by weight unlessPtherwise stated, i t th aqueous solutions being basic t There are ofcourse many forms of the invention litmus. Specific amines which havebeen found 7 other than these specific mbodiments.

to undergo this type of condensation with urea are diethylenetriamine,triethylenetetramine, Example Hemmethylenedwrea andbis-hexamethylenetriamine. The products An intimfite mixture of 115parts of hexaare useful in coating compositions and asintermemetfhylenedlamme (1 mol) and 180 Parts O c ysdiates for furtherreaction with formaldehyde to tallme urea (3 i' was heated at 130-140 c.for 5 fo -m thermo-setfing reshm e a period of 3 to 4 hours. The mixturebecame wh th a i r t ith urea, 1 an ncompletely liquid after thirtyminutes of heating phatic primary diamine, especially one wherein andthe fusion was accompanied by a rapid evoluthe amine groups areseparated by an aliphatic tion of ammonia which decreased in amount withhydrocarbon radical such as a polymethylene continued heating. At theend of two hours the 55 evolution of ammonia practically ceased, but,although solid, the mixture was subjected to an additional hour ofheating to insure complete reaction. The solid product was thendissolved in hot water and on cooling 180parts or a 90% yield ofhexamethylenediurea of M. P. 196 C. was obtained.

Example IL-Hezamethylenediurea Example I was repeated using 16 parts ofhexamethylenediamine (1 moi) and 8.5 parts of crystalline urea (1 mol).Thirteen and twotenths parts of hexamethylenediurea was obtained. Thiswas a yield of 96.5 per cent of the theoretical amount based on theurea. When the temperature is raised to 160 to 180 0., however, theseparticular proportions will begin to show some evidence of polymerformation.

It is important to note from the foregoing two examples that the yield,with proper temperature control in Example II, is practicallyquantitative in the sense of the equation given above regardless of therelative proportion of the diamine and the urea. The diurea alone seemsto be formed although in Example I the urea is present in 50% excess,and although in Example 11 the diamine is present in 100% excess of theamounts necessary for diurea formation.

' Example III .-Ethylenediurea A mixture of 75 parts of ethylenediamineand 233 parts of urea was intimately mixed and then heated under refluxat 130-140 C. for three hours. The mixture soon became liquid and arapid evolution of ammonia took place. When the evolution of ammonia waspractically complete, the mixture became solid. This solid product wascrystallized from boiling water and 179 parts or a 99% yield ofethylenediurea of M. P. 1934 C. was obtained.

Example IV.Decamethg lenediurea A finely ground mixture of 47 parts ofdecamethylenediamine and 47 parts of urea was heated at 130-140 C. forfour hours. The mixture did not become completely liquid but ammonia wasevolved at a rapid rate. This evolution practically ceased at thecompletion of four hours of heating and the mixture became solid. Thehard cake was then finely pulverized and the powder repeatedly extractedwith boiling alcohol to remove soluble by-products. Seventy-five partsor a 95% yield of decamethylenediurea M. P. 182-186 C. was obtained.

The invention has been illustrated above with polymethylenediamines. Forthe particular polymethylenediamines of the examples there may besubstituted any other polymethylenediamine, in-

pounds. Still other amines which may be used are p,p'-dlaminodiethylether, wW-diami-nodipropyle ether, p,p'-diam1nodiethyl sulfide,'y,'y'-d1- aminodipropyl sulfide, and 1,2-di(aminomethyl)dioxane. Theseprimary diamines yield crystalline diureas analogous to those of theexamples. the greatest facility.

The temperature of reaction may be varied from about to about 200 C.,but the reaction generally proceeds most smoothly at about to C.Temperatures above the latter point sometimes cause some resinificationand hence are less satisfactory. The higher the temperature employed,the faster the reaction proceeds, but usually the lower the yield due tothe loss of urea through decomposition. The time of heating is somewhatdependent on the temperature of the reaction, but usually 3 or 4 hoursof heating is necessary to complete the reaction as judged by thecessation of the evolution of ammonia.

The amounts of diamine and urea employed may be varied within widelimits without materially afiecting the final outcome of the reac tion,i. e., the formation of the diurea. However, it is advantageous toemploy two mols of urea for one mol of diamine. Urea liquor can be usedinstead of crystalline urea but allowance must be made for theimpurities. Instead of the free diamines, diamine salts such as thehydrochloride, acetate, carbonate, or lactate may be used. If desired acurrent of inert gas such as hydrogen, nitrogen, carbon monoxide orwater gas may be passed through or over the reaction mixture,particularly during the latter stages of the process, to facilitateremoval of ammonia. The process may also be carried out to advantage inthe presence of inert liquid diluents, particularly phenols such asphenol, the cresols, and hydroxydiphenyl, which are solvents for thereactants but not for the product.

The reaction can be carried out with or without agitation. Catalystssuch as aluminum chloride, stannic chloride, ferric chloride, borontrifluoride, etc., may be employed if so desired.

The crystalline monomeric aliphatic diureas described herein are alsouseful as intermediates for resins of the ureaformaldehyde type. Oneprocess for making such resins consists in carrying out a preliminarycondensation between, for example, hexamethylenediurea and formaldehydein the presence of an excess of a monohydric alcohol, such as isobutylalcohol, at a pH of 8-9 and a temperature of 90 to 100 C.,

followed by a final condensation in an acid medium, at refluxtemperature. The final condensation is performed in such a manner thatthe water formed during the condensation can be removed from the sphereof action, thus causing the reaction to go to completion, and showingthat the alcohol takes part in the condensation and is an essentialingredient of the resin, The heat-hardening resins, thus obtained in analcohol soluble form, set to a tough glossy film with exceptional waterand alkali resistance. Films cast from a 50% isobutanol solution air dryand become tack-free in two hours at room temperature or in 5 minutes at100 C.

In Examples I, II and III, the polyurea is iso lated by crystallizationfrom water. In Example IV, the polyurea is isolated by dissolving outthe impurities. The invention is not limited to these methods ofpurification. The product may be extracted with dilute hydrochloric orsulfuric The polymethylenediamines do so with acids, and subsequentlyprecipitated with alkali, or it may be crystallized from an organicsolvent, such as an alcohol, a ketone, an ester, an arcmatichydrocarbon, or an aliphatic hydrocarbon.

In the specification and claims the term aliphatic includescycloaliphatic as well as open chain aliphatic. The term aliphaticprimary diamine in the claims represents a compound containing two amino.(NHz) groups separated by an aliphatic radical. Similarly the termaliphatic primary polyamine represents a compound containing a pluralityof amino (NHz) groups attached to an aliphatic radical.

The process described herein is a simple, direct method for obtainingaliphatic diureas applicable readily on a commercial scale. It is acomparatively inexpensive process.

The above description and examples are intended to be illustrative only.Any modification of or variation therefrom which conforms to the spiritof the invention is intended to be included within the scope of theclaims.

I claim:

1. Process of preparing aliphatic polyureas which comprises heating ureawith a member of the class consisting of aliphatic polyamines having atleast one hydrogen atom on each amino nitrogen atom and acid additionsalts thereof at a temperature sufficient to cause the evolution ofammonia but below that at which decomposition takes place, andthereafter isolating the polyurea.

2. Process of preparing aliphatic polyureas which comprises heating analiphatic polyamine having at least one hydrogen atom on each aminonitrogen atom and urea at a temperature suilicient to cause theevolution of ammonia but below that at which decomposition takes place,continuing the heating until no further ammonia is evolved, andthereafter isolating the polyurea.

3. Process of preparing aliphatic diureas which comprises heating ureawith an aliphatic primary diamine at a temperature suificient to causethe evolution of ammonia but below that at which decomposition takesplace until ammonia ceases to be evolved and thereafter isolating thediurea.

4. Process of preparing polymethylenediureas which comprises heatingurea with a polymethylenediamine having at least one hydrogen atom oneach amino nitrogen atom at a temperature sufiicient to cause theevolution of ammonia but below that at which decomposition takes placeuntil ammonia ceases to be evolved and thereafter isolating thepolymethylenediurea.

5. Process of preparing polymethylenediureas which comprises reactingurea with a polymethylenediamine having at least one hydrogen atomattached to each amino-nitrogen .atom, in a molar ratio of about two toone, at 120 to 160 C. until evolution of ammonia substantially ceases.

6. Process of preparing aliphatic polyureas which comprises heating analiphatic primary polyamine and urea at a temperature sufficient tocause the evolution of ammonia but below that at which decompositiontakes place. continuing the heating until no further ammonia is evolved.and thereafter isolating the polyurea- 7. Process of preparingpolymethylenediureas which comprises heating urea at a temperaturesufficient to cause the evolution of ammonia but below that at whichdecomposition takes place with a primary polymethylenediamine untilammonia ceases to be evolved and thereafter isolating thepolymethylenediurea.

8. Process of preparing polymethylenediureas which comprises reactingurea with a primary polymethylenediamine in a molar ratio of about twoto one, at 120-160 C., until evolution of ammonia substantially ceases.

9. Process of preparing aliphatic polyureas which comprises heating ureawith a member of the class consisting of aliphatic primary polyaminesand addition salts thereof, at a temperature sufiicient to cause theevolution of ammonia but below that at which decomposition takes place,and thereafter isolating the polyurea.

10. Process of preparing aliphatic polyureas which comprises heatingurea with an aliphatic primary polyamine at a temperature sufficient tocause the evolution of ammonia but below that at which decompositiontakes place until ammonia ceases to be evolved and thereafter isolatingthe polyurea.

11. Process of preparing aliphatic polyureas which comprises heatingurea with an aliphatic primary diamine at a temperature suflicient tocause the evolution of ammonia but below that.

at which decomposition takes place until ammonia ceases to'be evolvedand thereafter isolating the polyurea.

12. Process of preparing polymethylenediureas which comprises heatingurea with an aliphatic primary polymethylenediamine at a temperaturesufiicient to cause the evolution of ammonia but below that at whichdecomposition takes place until ammonia ceases to be evolved andthereafter isolating the polyurea.

13. Process of preparing aliphatic polyureas which comprises heating, at100200 C., urea with a member of the class consisting of aliphaticprimary polyamines and addition salts thereof and thereafter isolatingthe polyurea.

14. Process of preparing aliphatic polyureas which comprises heating, at100-200 C., urea with an aliphatic primary polyamine until ammoniaceases to be evolved and thereafter isolating the polyurea.

15. Process of preparing aliphatic polyureas which comprises heating, atNil-200 C., urea with an aliphatic primary diamine until ammonia ceasesto be evolved and thereafter isolating the polyurea.

10. Process of preparing polymethylenediureas which comprises heating,at 100-200 C., urea with an aliphatic primary polymethylenediamine untilammonia ceases to be evolved and thereafter isolating the polyurea. V

17. Process of preparing aliphatic diureas which comprises heating ureaat IOU-200 C. with an aliphatic diprimary diamine until ammonia ceasesto be evolved and thereafter isolating the diurea.

HAROLD WILFRED ARNOLD.

